Regenerative medicine includes therapies designed to aid the repair, replacement, or regeneration of damaged cells, tissues, or organs. One branch of regenerative medicine includes therapies that rely on embryonic stem cells (ES), which have the potential to give rise to a diverse range of cell types. ES-based therapies have the promise of treating a variety of health conditions including degenerative diseases, proliferative diseases, hereditary diseases, injuries, and organ failures. However, the progress of such therapies has been hindered by a range of factors including the possibility of immune rejection of ES cells derived from a donor who is immunologically incompatible with the recipient, as well as ethical and legal concerns.